1. Field of the Invention
The present invention relates to an apparatus for measuring an electroencephalogram and a method for driving the apparatus, and more particularly, to an electroencephalogram (EEG) measuring apparatus for measuring a pure electroencephalogram without combined noise waves, by considering the ground state of an experimentee and a method for driving the apparatus.
2. Description of the Related Art
An electroencephalogram which enables to spatiotemporally recognize the activities of a brain is a leading living body signal, and is widely used in clinical research and brain function researches. Recently, the electroencephalogram is used in bio-feedback in which the mental states of a user is improved through modulation of an electroencephalogram by an external stimulus. Also, using the living body signals such as the electroencephalogram, an eletrocardiogram, or Galvanic Skin Resistance (GSR), the emotion of an individual is evaluated. In addition, the electroencephalogram is applied to a Brain-Computer Interface (BCI) field which aims to achieve a direct interface between humans and machines through an electroencephalogram without using languages or body actions.
However, in measuring a human electroencephalogram, noise waves, including an electromyogram generated by human actions, an electrooculogram generated by eye movement, an electrocardiogram, a slow wave generated by respiration and perspiration, and a signal generated by skin deformation due to an electrode attached for measuring an electroencephalogram, are combined into the electroencephalogram. If this noise waves are combined with the electroencephalogram, the electroencephalogram of an experimentee cannot be accurately measured.
Therefore, a prior art method which removes noise waves combined by human actions is disclosed in U.S. Pat. No. 4,550,736, entitled “Movement artifact detector for sleep analysis”. According to the method, in order to remove noise waves combined by actions when a sleeping electroencephalogram is measured, it is determined that noise waves are combined if any one of the following three components is detected, including an electromyogram component (equal to or greater than 30 Hz, 18 μV) which has a greater value than the electroencephalogram, a component (equal to or greater than 30 Hz, −9 μV˜9 μV) which is generated when an electroencephalogram amplifier returns to a normal state after data collection is temporarily stopped due to a disorder in the electroencephalogram amplifier, and a noise wave component (equal to or less than 1.2 Hz, equal to or greater than 200 μV) due to respiration or perspiration.
However, the method does not consider the facts that the amplitude of an electroencephalogram changes by individuals, and the frequency component of an electroencephalogram changes differently according to physical and cognitive information processing.
Also, there is a method for removing noise waves generated by actions, using a sensor, but the method needs additional cost.